Various wind turbines and air screws for the generation of electricity have been proposed. The present disclosure relates to a vertical axis type of air turbine, more commonly known as a “vertical” wind turbine. One difficulty with vertical rotating blades is that about half of the blades are driving the turbine at any time whereas the opposite half or “dead” blades slow the rotation down due to drag. These dead or non-driving blades are return blades trying to move upwind during part of their rotational cycle against the direction of the prevailing wind. This drag can significantly reduce the power output and energy conversion efficiency of vertical wind turbines.
Another difficulty is that the torque on a vertical turbine blade can be compromised in that at low wind speeds it may not take much load to stop the turbine from turning while at high speeds the rotational velocity of a load-uncompensated turbine can become very high causing instability and excessive vibration. Even at high speeds the angular momentum of an uncompensated turbine can be insufficient to maintain an even speed when load is applied.